The present invention relates generally to fluid pumps. More particularly, the present invention relates to a fluid pump with a single sensor configured to detect an overheat condition in either the pump head or the motor driving the pump head.
Fluid pumps with integral motors, such as so-called xe2x80x9ccannedxe2x80x9d pumps, are generally employed in a variety of applications. For example, fluid motor pumps are often used to move potable fluids, such as water, in beverage dispensing machines. Motors employed in such pumps are often run xe2x80x9cwetxe2x80x9d in that the pumped fluid circulates through the motor. To protect the motor stator windings from the fluid, a barrier can or liner is positioned in the motor air gap. Unfortunately, the barrier can has the undesirable effect of increasing the motor air gap with a corresponding reduction in motor performance. Depending on the type of pump, the barrier can be subjected to rather high fluid pressures. To maintain the barrier can""s structural integrity, the can is configured to have relatively thick walls which can withstand the forces exerted by the pressurized fluid with little or no deformation of the can. In order to maintain proper running clearances, the motor air gap must be increased in direct proportion to the can wall thickness. To accommodate the increase in air gap, the motor must typically be upsized to keep motor performance at a desired level.
What is needed, therefore, is a barrier can for a canned motor pump that reduces the motor air gap of prior art canned motor pumps.
The present invention achieves its objectives by providing an apparatus for protecting a fluid pump motor. The apparatus includes an electric motor for driving a pump head, such as a rotary vane pump head, to pressurize a fluid. The electric motor includes a stator with one or more magnetic field producing elements for producing a magnetic field in response to a flow of electrical current through the one or more magnetic field producing elements, and a rotor having a rotor shaft for driving the pump head in response to the magnetic field produced by the stator. A motor air gap defined between the stator and the rotor receives pressurized fluid from the pump head. A liner is positioned in the air gap to inhibit pressurized fluid entering the air gap from contacting the one or more magnetic field producing elements of the stator. The liner has a thin liner wall that deforms during operation of the apparatus to bear against the one or more magnetic field producing elements of the stator for structural support as a result of loading imparted by the pressurized fluid on the liner wall.
In a preferred embodiment, the electric motor includes and end cap for closing one end of the motor. In this embodiment, the liner wall may include a portion that deforms to bear against the end cap for structural support as a result of loading by the pressurized fluid.
The liner may be fabricated as a single metal part using a deep drawing process to produce a liner with opposed open and closed ends with a substantially uniform cross-section between the open and closed ends.
To protect the rotor laminations from pressurized fluid entering the motor air gap, the rotor may be include a rotor barrier can which seals the rotor laminations from the fluid.